1. Field of the Invention
This invention pertains to the formation of threaded metal parts, to the method of forming, to the tooling employed, and to the resulting articles.
2. Description of the Prior Art
In the manufacture of threaded metal parts the conventional practice has been either to machine or roll the threads. This has been a major factor in the cost of such parts, because of the tooling, time, equipment, and material involved in such operations. The cost of threading is of particular significance where a part is adapted for economical production without machining, except for a threaded section. For example, there may be a part which in most aspects is adapted for production by stamping, but require a threaded portion for connecting it to an associated item. Conventionally, it is necessary either to machine the entire part or to stamp a portion of it and weld on a separately machined threaded element. In either event, the cost of the part is greatly increased. Additionally, when parts must be secured together, such as by welding, there is always a question as to the reliability of the connection and some of the parts may fail because of an improper weld.
There have been some efforts to produce threaded parts in another way, such as by engaging them with a die having a thread contour and then bending the part to assume a cylindrical shape. However, for anything approaching a part having a well-formed thread, accurately shaped and of adequate strength, these efforts have been unsucessful. Hence, the traditional machining techniques have remained predominant in the metal forming art.